In the next grant period we will focus on understanding the Mo-catalyzed reduction in as much detail as possible, and in particular, what is the circumstance that leads to a breakdown in catalytic turnover of dinitrogen to ammonia. In the process we want to determine to what extent the successful system resembles the reduction of dinitrogen by the natural FeMo nitrogenase, and therefore attempt to build a case indirectly for or against reduction of dinitrogen at Mo in the natural FeMo system. Part of this effort will consist of catalytic reduction of substrates other than dinitrogen under conditions where dinitrogen is reduced in the well-defined system. We will continue to design new trianionic triamidoamine ligands that would allow reduction of dinitrogen under mild conditions at molybdenum, and we want to expand the chemistry of triamidoamine ligands to iron and ruthenium. We also want to design dianionic and monoanionic ligands for vanadium, iron, and ruthenium and want to explore methods of incorporating nitrogen into organic molecules, either directly, or via reactions that are linked to ammonia formation. The reduction of dinitrogen to ammonia is perhaps the most complex metalloenzyme-catalyzed process in nature and is essential for all life. To learn how dinitrogen reduction can be accomplished under mild conditions with a well-defined catalyst is one of the grand challenges. In the long run a reduction at room temperature and pressure could lead to an enormous savings in energy for ammonia production and to an understanding of catalytic principles that may help us design other catalytic processes or understand other catalytic reactions in biology.